1. Field of the Invention
The present invention generally relates to a weighing apparatus for measuring the weight of articles to be weighed and, more particularly, to the adjustment of a filter used in the weighing apparatus for removing a vibratory component contained in a weight signal.
2. Description of the Prior Art
Of the weighing apparatuses for measuring the weight of articles to be weighed, a combination weighing apparatus is known in which a combination calculation of respective weights of the articles to be weighed which have been supplied into a plurality of weighing hoppers is performed to provide a product having a predetermined weight. In this combination weighing apparatus, since the natural vibration peculiar to a weighing mechanism itself having an associated weighing hopper and an external vibration brought about mainly by vibration of the floor tend to be imposed as a vibration component on a weight signal outputted from each of the weighing hoppers, the use of a filter (a low-pass filter) in association with each of the weighing hoppers is necessitated to remove the vibration component to secure a weighing accuracy. In general, the frequency of the natural vibration is higher than that of the external vibration.
The filter of the kind described above is of a nature that once the filter constant determinative of the filter characteristics (cut-off frequency and/or damping characteristic) is determined, a filter response time can be fixed. In other words, if the capability of damping vibrations is increased by lowering the cut-off frequency, the response time can be increased, but if the capability of damping vibrations is lowered by increasing the cut-off frequency, the response time can be reduced. In view of this, the filter that can be employed in the weighing apparatus of the kind referred to above is required to be of a type having such a filter characteristic capable of damping the vibration component down to a level which will no longer affect the weighing accuracy and also having a short response time.
However, since the vibration component of the weight signal varies depending on weighing conditions of the weighing apparatus and/or conditions under which the weighing apparatus is installed, the solution hitherto taken is to install the weighing apparatus at a site of installation, to conduct a series of tests through trial and error with the filter characteristic being varied while articles to be weighed are actually supplied into the weighing apparatus and finally to select one of filters which has a vibration damping capability effective to secure the weighing accuracy and also having a short filter response time. Accordingly, an adjustment of the filter was a time-consuming work. Since the combination weighing apparatus requires the use of a plurality of weighing mechanisms, adjustment of the filter is required for each of the weighing mechanisms, resulting in extremely timeconsuming and complicated procedures.